A linear glucan was produced by Lactobacillus sake L-7 isolated from homemade sausage. Cultivation of the strain in Man–Rogosa–Sharpe(MRS) medium containing 50 g/L sucrose yielded 5.3 g/L of purified exopolysacchari...A linear glucan was produced by Lactobacillus sake L-7 isolated from homemade sausage. Cultivation of the strain in Man–Rogosa–Sharpe(MRS) medium containing 50 g/L sucrose yielded 5.3 g/L of purified exopolysaccharide(EPS). The EPS was characterized by gas chromatography(GC), Fourier-transform infrared(FT-IR) spectroscopy, high-performance sizeexclusion chromatography(HPSEC), nuclear magnetic resonance(NMR) spectroscopy, and scanning electron microscopy(SEM). The monosaccharide composition of the EPS was glucose, and its molecular weight was 1 × 10~7 Da. The FT-IR and NMR spectra revealed that the L-7 EPS was a linear glucan with α-(1 → 6) glucosidic bonds. SEM images of the dried EPS revealed a hollow tubular structure. The water solubility index and water holding capacity of L-7 EPS were 96 and 272%, respectively. The results of hydrolysis indicated that L-7 EPS was not susceptible to hydrolysis by physiological barriers and can be used as a soluble dietary fiber with health benefits. All these characteristics suggest that L-7 EPS might have potential applications in the food, cosmetic, and pharmaceutical industries.展开更多
In this study,we aimed to examine the inhibitory effect of PA003,a Pediococcus acidilactici that produces lactic acid and antimicrobial peptides pediocin,on pathogenic biofilm formation on abiotic surfaces.PA003 and p...In this study,we aimed to examine the inhibitory effect of PA003,a Pediococcus acidilactici that produces lactic acid and antimicrobial peptides pediocin,on pathogenic biofilm formation on abiotic surfaces.PA003 and pathogens(Escherichia coli,Salmonella enterica serovar Typhimurium,Staphylococcus aureus and Listeria monocytogenes) were used to evaluate auto-aggregation,hydrophobicity,biofilm formation and biofilm formation inhibition on stainless steel,polyvinyl chloride and glass slides in terms of exclusion,displacement and competition.The results showed the highest auto-aggregation abilities were observed for one of the E.coli strains EAggEC(E58595) and the highest hydrophobic strain was observed with EPEC(E2348/69)(51.9%).The numbers of biofilm cells of E.coli,S.Typhimurium,S.aureus and L.monocytogenes on stainless steel,polyvinyl chloride and glass slide coupons were effectively reduced by approximately 4log CFU/coupon.These results demonstrate that lactic acid bacteria can be used as an alternative to effectively control the formation of biofilms by food-borne pathogens.展开更多
A strain with high production of exopolysaccharide(EPS) was isolated from dried milk cake(a traditional fermented food from Inner Mongolia). The strain was called N21 and later identified as Leuconostoc citreum( Leu. ...A strain with high production of exopolysaccharide(EPS) was isolated from dried milk cake(a traditional fermented food from Inner Mongolia). The strain was called N21 and later identified as Leuconostoc citreum( Leu. citreum). The strain was cultured in Man-Rogosa-Sharpe medium containing 50 g/L of sucrose for 48 h at 30 °C and the EPS purified, with a yield of 24.5 g/L. An average molecular weight of 6.07 × 10~6 g/mol was determined by high-performance size-exclusion chromatography. The structure of the purified EPS was investigated through gas chromatography, ~1H and ^(13)C nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. The results demonstrated a polysaccharide composed of D-glucopyranose units in a linear chain with consecutive α(1 → 6) linkages. No branching was found in the structure of the exopolysaccharide. The purified EPS showed high water solubility and emulsibility. Based on the thermogravimetric curve, the degradation temperature of the EPS was 308.47 °C, which suggested that the dextran in the study exhibited high thermal stability. The results indicated that Leu. citreum N21 could be widely used to produce linear EPS and that the EPS has potential applications in food science and processing as a food additive.展开更多
A great amount of foodborne pathogens were Gram-positive(G+) bacteria, a threat to public health. In this study, considering the binding ability of nisin towards G+ bacteria and the stable fluorescent ability of EGFP ...A great amount of foodborne pathogens were Gram-positive(G+) bacteria, a threat to public health. In this study, considering the binding ability of nisin towards G+ bacteria and the stable fluorescent ability of EGFP protein, a fluorescent nisin–EGFP protein probe was constructed by a gene engineering method. Nisin and EGFP were used as the receptor and fluorophore, respectively, to detect G+ bacteria. The nisin and egfp gene were amplified separately according to the sequence published in Gen Bank using unique primers. The two genes were cloned into a pET-28b(+) vector resulting in apET-28b(+)–nisin–egfp vector. The vector was transferred into Escherichia coli(E. coli) BL21(DE3) for expression. The expressed protein was extracted, purified by a Ni–NTA column, and then tested by the SDS-PAGE method to confirm its molecular weight. Listeria monocytogenes(L.monocytogenes), Staphylococcus aureus(S. aureus), and Micrococcus luteus(M. luteus) were used as the representations of G+ bacteria. E. coli O157, representing the gram-negative(G-) bacteria, was used as a negative control. The binding specificity of the recombinant protein was performed on two types of bacteria and then detected through fluorescent microscopy. The results indicated that the nisin–EGFP probe could detect G+ bacteria at 10~8CFU/mL.展开更多
The objective of this study was to describe the fecal microbiota succession of piglets from birth to postweaning by pyrosequencing.The dominant bacterial phyla were Bacteroidetes,Firmicutes,Proteobacteria,and Fusobact...The objective of this study was to describe the fecal microbiota succession of piglets from birth to postweaning by pyrosequencing.The dominant bacterial phyla were Bacteroidetes,Firmicutes,Proteobacteria,and Fusobacteria,although the composition of the fecal microbiota changed as the piglets grew.Bacteroides,Parabacteroides,Prevotella,Lactobacillus,unclassified Lachnospiraceae,Ruminococcus,Oscillospira,Phascolarctobacterium,and Desulfovibrio were the core genera in the feces of piglets and existed from birth to post-weaning.Bacteroides was the most abundant at birth; however,the proportion of Bacteroides decreased as the piglets aged,while the proportion of Prevotella increased until it became the most abundant genus at the post-weaning stage.Principal coordinate analysis indicated that the microbial communities of piglet fecal samples from birth to postweaning could be separated into four groups according to the similarity of community composition.These corresponded to time points on day 0 (birth); day 7; days 14,21,and 28 (pre-weaning); and day 35 (post-weaning).This study suggests that the development of the intestinal microbiota in the piglet is a gradual and sequential process.This methodology establishes a basis for broader studies to investigate the microbiota of the piglet intestinal tract.展开更多
An antifungal lipopeptide iturin A with strong activity against Fusarium oxysporum was produced by honey isolated strain Bacillus amyloliquefaciens BH072. For large-scale biocontrol application, the antifungal effect ...An antifungal lipopeptide iturin A with strong activity against Fusarium oxysporum was produced by honey isolated strain Bacillus amyloliquefaciens BH072. For large-scale biocontrol application, the antifungal effect was deeply demonstrated by structure and mode of action. Cyclic structure and second structure were determined based on situ acid hydrolysis and Fourier Transformed-Infra Red (FT-IR) Spectra analysis. Structure of α-helix was predicted which might be associated with activity. Afterwards, antifungal mechanism of iturin A on F. oxysporum were investigated from fungal cell wall to the plasma membrane and finally to intracellular proteins by morphological, activity of alkaline phosphatase (AKP), conductivity, Malondialdehyde (MDA) and SDS-PAGE detection. Antifungal damage appears on not only the spore germination and mycelium growth of F. oxysporum, but also the leakage of cellular proteins. Moreover, growth of F. oxysporum could be inhibited in the presence of iturin A at a MIC of 2.5 mg/mL. Considered with its high production in previous work, B. amyloliquefaciens strain BH072 and iturin A might be a promising candidate for biocontrol.展开更多
基金supported by National Science and Technology Support Program of China (No. 2015BAD16B01)
文摘A linear glucan was produced by Lactobacillus sake L-7 isolated from homemade sausage. Cultivation of the strain in Man–Rogosa–Sharpe(MRS) medium containing 50 g/L sucrose yielded 5.3 g/L of purified exopolysaccharide(EPS). The EPS was characterized by gas chromatography(GC), Fourier-transform infrared(FT-IR) spectroscopy, high-performance sizeexclusion chromatography(HPSEC), nuclear magnetic resonance(NMR) spectroscopy, and scanning electron microscopy(SEM). The monosaccharide composition of the EPS was glucose, and its molecular weight was 1 × 10~7 Da. The FT-IR and NMR spectra revealed that the L-7 EPS was a linear glucan with α-(1 → 6) glucosidic bonds. SEM images of the dried EPS revealed a hollow tubular structure. The water solubility index and water holding capacity of L-7 EPS were 96 and 272%, respectively. The results of hydrolysis indicated that L-7 EPS was not susceptible to hydrolysis by physiological barriers and can be used as a soluble dietary fiber with health benefits. All these characteristics suggest that L-7 EPS might have potential applications in the food, cosmetic, and pharmaceutical industries.
基金Supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (2015BAD16B01)Tianjin Key Technology Research and Development Support Program (13ZCDNC01900)
文摘In this study,we aimed to examine the inhibitory effect of PA003,a Pediococcus acidilactici that produces lactic acid and antimicrobial peptides pediocin,on pathogenic biofilm formation on abiotic surfaces.PA003 and pathogens(Escherichia coli,Salmonella enterica serovar Typhimurium,Staphylococcus aureus and Listeria monocytogenes) were used to evaluate auto-aggregation,hydrophobicity,biofilm formation and biofilm formation inhibition on stainless steel,polyvinyl chloride and glass slides in terms of exclusion,displacement and competition.The results showed the highest auto-aggregation abilities were observed for one of the E.coli strains EAggEC(E58595) and the highest hydrophobic strain was observed with EPEC(E2348/69)(51.9%).The numbers of biofilm cells of E.coli,S.Typhimurium,S.aureus and L.monocytogenes on stainless steel,polyvinyl chloride and glass slide coupons were effectively reduced by approximately 4log CFU/coupon.These results demonstrate that lactic acid bacteria can be used as an alternative to effectively control the formation of biofilms by food-borne pathogens.
基金supported by the National Science and Technology Support Plan Project(No.2015BAD16B01)
文摘A strain with high production of exopolysaccharide(EPS) was isolated from dried milk cake(a traditional fermented food from Inner Mongolia). The strain was called N21 and later identified as Leuconostoc citreum( Leu. citreum). The strain was cultured in Man-Rogosa-Sharpe medium containing 50 g/L of sucrose for 48 h at 30 °C and the EPS purified, with a yield of 24.5 g/L. An average molecular weight of 6.07 × 10~6 g/mol was determined by high-performance size-exclusion chromatography. The structure of the purified EPS was investigated through gas chromatography, ~1H and ^(13)C nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. The results demonstrated a polysaccharide composed of D-glucopyranose units in a linear chain with consecutive α(1 → 6) linkages. No branching was found in the structure of the exopolysaccharide. The purified EPS showed high water solubility and emulsibility. Based on the thermogravimetric curve, the degradation temperature of the EPS was 308.47 °C, which suggested that the dextran in the study exhibited high thermal stability. The results indicated that Leu. citreum N21 could be widely used to produce linear EPS and that the EPS has potential applications in food science and processing as a food additive.
基金supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (No. 2015BAD16B01)TianjinKey Technology Research and Development Support Program (No. 13ZCDNC01900)
文摘A great amount of foodborne pathogens were Gram-positive(G+) bacteria, a threat to public health. In this study, considering the binding ability of nisin towards G+ bacteria and the stable fluorescent ability of EGFP protein, a fluorescent nisin–EGFP protein probe was constructed by a gene engineering method. Nisin and EGFP were used as the receptor and fluorophore, respectively, to detect G+ bacteria. The nisin and egfp gene were amplified separately according to the sequence published in Gen Bank using unique primers. The two genes were cloned into a pET-28b(+) vector resulting in apET-28b(+)–nisin–egfp vector. The vector was transferred into Escherichia coli(E. coli) BL21(DE3) for expression. The expressed protein was extracted, purified by a Ni–NTA column, and then tested by the SDS-PAGE method to confirm its molecular weight. Listeria monocytogenes(L.monocytogenes), Staphylococcus aureus(S. aureus), and Micrococcus luteus(M. luteus) were used as the representations of G+ bacteria. E. coli O157, representing the gram-negative(G-) bacteria, was used as a negative control. The binding specificity of the recombinant protein was performed on two types of bacteria and then detected through fluorescent microscopy. The results indicated that the nisin–EGFP probe could detect G+ bacteria at 10~8CFU/mL.
基金supported by the Open Funding Project of the Key Laboratory of Systems Bioengineering in Tianjin,Ministry of Education of China(No.20160110)
文摘The objective of this study was to describe the fecal microbiota succession of piglets from birth to postweaning by pyrosequencing.The dominant bacterial phyla were Bacteroidetes,Firmicutes,Proteobacteria,and Fusobacteria,although the composition of the fecal microbiota changed as the piglets grew.Bacteroides,Parabacteroides,Prevotella,Lactobacillus,unclassified Lachnospiraceae,Ruminococcus,Oscillospira,Phascolarctobacterium,and Desulfovibrio were the core genera in the feces of piglets and existed from birth to post-weaning.Bacteroides was the most abundant at birth; however,the proportion of Bacteroides decreased as the piglets aged,while the proportion of Prevotella increased until it became the most abundant genus at the post-weaning stage.Principal coordinate analysis indicated that the microbial communities of piglet fecal samples from birth to postweaning could be separated into four groups according to the similarity of community composition.These corresponded to time points on day 0 (birth); day 7; days 14,21,and 28 (pre-weaning); and day 35 (post-weaning).This study suggests that the development of the intestinal microbiota in the piglet is a gradual and sequential process.This methodology establishes a basis for broader studies to investigate the microbiota of the piglet intestinal tract.
文摘An antifungal lipopeptide iturin A with strong activity against Fusarium oxysporum was produced by honey isolated strain Bacillus amyloliquefaciens BH072. For large-scale biocontrol application, the antifungal effect was deeply demonstrated by structure and mode of action. Cyclic structure and second structure were determined based on situ acid hydrolysis and Fourier Transformed-Infra Red (FT-IR) Spectra analysis. Structure of α-helix was predicted which might be associated with activity. Afterwards, antifungal mechanism of iturin A on F. oxysporum were investigated from fungal cell wall to the plasma membrane and finally to intracellular proteins by morphological, activity of alkaline phosphatase (AKP), conductivity, Malondialdehyde (MDA) and SDS-PAGE detection. Antifungal damage appears on not only the spore germination and mycelium growth of F. oxysporum, but also the leakage of cellular proteins. Moreover, growth of F. oxysporum could be inhibited in the presence of iturin A at a MIC of 2.5 mg/mL. Considered with its high production in previous work, B. amyloliquefaciens strain BH072 and iturin A might be a promising candidate for biocontrol.
